Original Message:
Sent: 05-25-2023 16:02
From: David Love
Subject: Baldwin SD Touchweight Quandry
I believe the issue is primarily that some individuals are striving for relevance, although I personally am focused on following Nick Gravagne's Sage advice and reducing my neurotic tendencies. I suppose I'll have to be satisfied with that.
The problem, Chris, is that no technicians use units of inertia, not even those capable of understanding it. Even individuals like the late Darrell Fandrich and certified engineer John Rhodes developed a concept unrelated to units of inertia, but rather something simpler using static measurements
David Stanwood's system, which many people utilize, also derives inertia from a series of static measurements. His objective is to achieve a specific inertia target by combining data such as front weight, strike weight, action leverage, and balance weight. These parameters, when met according to his system, result in a manageable level of inertia. It's worth noting that pianos inherently have higher inertia in the bass due to the decreasing mass of the hammers, but that's a separate issue. As a side note, for those interested in achieving a uniform level of inertia, it might be worth considering the addition of lead weights at opposite positions and equal values on the front and back of the keys to increase key inertia. However, currently we tend to use the minimum number of weights necessary to attain a specific balance weight. Consequently, the contribution of the key to the overall inertia is less significant compared to leverage and hammer mass.
Therefore, we aim for specific strike weights with certain action ratios to achieve an acceptable level of inertia. If you're unfamiliar with the process, you can become a Stanwood licensed installer to learn and apply these techniques, which can be valuable credentials in the market. David Stanwood and others, including myself, have been generous in sharing this information and offering a practical approach without delving into relatively useless numerical calculations of inertia.
While I appreciate your desire to demonstrate your engineering expertise, it holds little practical importance in what we actually do.
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 05-24-2023 18:54
From: Chris Chernobieff
Subject: Baldwin SD Touchweight Quandry
If that were true, then threads like this wouldn't exist.
-chris
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Chernobieff Piano Restorations
All the elements are known, and yet no combination there of creates life. Yet we are here.
865-986-7720 (text only please)
Original Message:
Sent: 05-24-2023 18:35
From: David Love
Subject: Baldwin SD Touchweight Quandry
Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 05-24-2023 18:13
From: Chris Chernobieff
Subject: Baldwin SD Touchweight Quandry
Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum, then all of the variable of masses and leverages in a piano action can be precisely expressed.
-chris
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Chernobieff Piano Restorations
All the elements are known, and yet no combination there of creates life. Yet we are here.
865-986-7720 (text only please)
Original Message:
Sent: 05-24-2023 16:37
From: David Stanwood
Subject: Baldwin SD Touchweight Quandry
Front Weight + Balance Weight is not an inertia measurement. It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.
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David Stanwood RPT
Stanwood Piano Innovations Inc.
West Tisbury MA
(508) 693-1583
Original Message:
Sent: 05-24-2023 09:25
From: Chris Chernobieff
Subject: Baldwin SD Touchweight Quandry
Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight and Balance Weight.
Why put a wheel on a balance scale to know how fast it will roll down a hill?
With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.
-chris
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Chernobieff Piano Restorations
All the elements are known, and yet no combination there of creates life. Yet we are here.
865-986-7720 (text only please)
Original Message:
Sent: 05-24-2023 08:53
From: John Pope
Subject: Baldwin SD Touchweight Quandry
My friend and fellow RPT Russell Schmidt asked for my input on rebuilding the action on a Baldwin SD-1 (1937), the predecessor of the SD-6, the predecessor of the SD-10. It was rebuilt about 30 years ago with a new soundboard, block etc. by the late Claire Davies, a well respected local rebuilder.
The complaint has been that the piano is difficult to play and has no dynamic range. Indeed, when I played it I immediately thought, "Boy ,there's a lot of inertia in there." It feels very heavy. It seemed like a classic case of too-heavy hammers. I expected to find keys full of lead to compensate. Measurably, the touch is quite light (45 to 50 DW).
However, the keys turned out to have little lead and hammer strike weight is in medium range.
I did David Stanwood's test of temporarily setting C4 front weight to 27 and finding the hammer strike weight that gets you 38 balance weight. The existing C4 hammer tested to be the perfect weight.
SOMETHING ELSE IS GOING ON HERE!
I happened to have a set of original hammers and shanks from a 1965 SD-6 and compared the two. The hammers on our SD-1 are further out on their shanks. Also, note 1 measures to be further out on its shank than #88. Have the bass strike points wandered from their original specs?
Any other ideas?
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John Pope
University of Kentucky School of Music
Lexington, KY
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